docs: adding more details for monitoring and operations

docs/infrastructure/monitoring/prometheus_curl.md

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+# Prometheus scrape target metric names
+
+Here are ready‑to‑run **cURL** commands you can use to query each Prometheus scrape target and list the metric names they expose.  
+The Prometheus HTTP API endpoint `http://localhost:9090/api/v1/label/__name__/values` returns all metric names currently known for the target’s job/instance.
+
+---
+
+## 1. Chat (`http://chat:3000/metrics`)
+
+```bash
+curl -s 'http://localhost:9090/api/v1/label/__name__/values?match[]={job="chat",instance="chat:3000"}' | jq .
+```
+
+## 2. NGINX exporter (`http://nginx-exporter:9113/metrics`)
+
+```bash
+curl -s 'http://localhost:9090/api/v1/label/__name__/values?match[]={job="nginx",instance="nginx-exporter:9113"}' | jq .
+```
+
+## 3. Node exporter (`http://node-exporter:9100/metrics`)
+
+```bash
+curl -s 'http://localhost:9090/api/v1/label/__name__/values?match[]={job="node",instance="node-exporter:9100"}' | jq .
+```
+
+## 4. Playout (`http://playout:8081/metrics`)
+
+```bash
+curl -s 'http://localhost:9090/api/v1/label/__name__/values?match[]={job="playout",instance="playout:8081"}' | jq .
+```
+
+## 5. Postgres exporter (`http://postgres-exporter:9187/metrics`)
+
+```bash
+curl -s 'http://localhost:9090/api/v1/label/__name__/values?match[]={job="postgres",instance="postgres-exporter:9187"}' | jq .
+```
+
+## 6. Prometheus itself (`http://prometheus:9090/metrics`)
+
+```bash
+curl -s 'http://localhost:9090/api/v1/label/__name__/values?match[]={job="prometheus",instance="prometheus:9090"}' | jq .
+```
+
+## 7. Redis exporter (`http://redis-exporter:9121/metrics`)
+
+```bash
+curl -s 'http://localhost:9090/api/v1/label/__name__/values?match[]={job="redis",instance="redis-exporter:9121"}' | jq .
+```
+
+---
+
+### How it works
+
+- `http://localhost:9090` – address of your Prometheus server.
+- `/api/v1/label/__name__/values` – API call that lists _all_ metric names (`__name__` label) known to Prometheus.
+- `match[]` – a selector that restricts the result to the specific `job` and `instance` you care about.
+- `-s` – silent mode (no progress meter).
+- `| jq .` – pretty‑prints the JSON response (optional but handy).
+
+Running any of these commands will output a JSON array like:
+
+```json
+[
+  "up",
+  "process_cpu_seconds_total",
+  "http_requests_total",
+  ...
+]
+```
+
+which is the full set of metrics currently being scraped from that target. Adjust the Prometheus host/port if it differs from `http://localhost:9090`.